Remove test globals from hydrogen-react tests

[cartogram]

WHY are these changes introduced?

Bringing some consistency to our packages.

WHAT is this pull request doing?

I took a poll and discovered we prefer explicit imports of test methods such as describe, it and expect. This PR imports the necessary methods in the hydrogen-react package.

HOW to test your changes?

Green CI

Post-merge steps

Checklist

• I've read the Contributing Guidelines
• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've added a changeset if this PR contains user-facing or noteworthy changes
• I've added tests to cover my changes
• I've added or updated the documentation

[github-actions]

We detected some changes in packages/*/package.json or packages/*/src, and there are no updates in the .changeset.
If the changes are user-facing and should cause a version bump, run npm run changeset add to track your changes and include them in the next release CHANGELOG.
If you are making simple updates to examples or documentation, you do not need to add a changeset.

[juanpprieto]

👍🏼

[frehner]

Thanks!